Project Summary Circulating tumor cells (CTCs), considered to be the seeds of metastasis, are rare cells that detach themselves from primary tumors and travel in the blood as residual disease, potentially colonizing as metastases in distant organs. Therefore, detection of CTCs may serve as a tool for early detection of residual disease, relapse, and metastasis. Although available CTC assays detect epithelial markers such as EpCAM and cytokeratins, they are ineffective in detecting CTCs from non-epithelial tumors such as melanoma, neuroblastoma, and sarcomas. Innovative tools for universal CTC detection are needed. The PI has discovered that cell surface vimentin (CSV) is expressed on the surface of CTCs but not normal cells in peripheral blood of patients with different types of tumors. This CSV is detectable by using an antibody (84-1) developed by the PI. Significantly, this CSV is primarily found on freshly isolated metastatic tumor cells. The goal of this application is to develop a universal CTC detection chip (U-CTChip) and to perform automated CTC capture using this U-CTChip. Current CTC research is largely focused on the association of CTCs with survival, but we believe that CTCs have other clinical applications, such as early detection of tumor relapse and monitoring the efficacy of maintenance therapy. In our preliminary studies of our CSV-CTC capture tool, we observed that change in CTC numbers over time (from checkup to checkup) was associated with tumor relapse and response to maintenance therapy in neuroblastoma. The second goal of the proposed project is to investigate these two novel clinical applications using U-CTChip.